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Abstract

A central aspect of physical activity (PA) and sedentary behavior (SB) research is accurate assessment in the context of disease outcomes. The primary objectives were to evaluate the convergent validity and test-retest reliability of the ActiGraph® GT3X+ (AG) and ActivPAL3® (AP) accelerometers. Participants were from the Breast Cancer and Exercise Trial in Alberta (n=225) and wore both monitors concurrently during waking hours for seven days. When comparing AG Vector Magnitude (VM) and Vertical axis (VT) with AP, all measures of PA were statistically significantly different with the exception of moderate activity between AG (VM) and AP (p=0.15). No statistically significant difference occurred between AP and AG (VM) or (VT) for time in SB with p=0.48 and p=0.27, respectively. Intraclass correlation coefficients (ICC) ranged from 0.66 to 0.93 for moderate and sedentary time by AG (VT), respectively. Despite small mean differences at the group level, limits of agreement suggest these devices cannot be used interchangeably.